Visualization of Layers Within a Convolutional Neural Network Using Gradient Activation Maps
Bibliographic record
Abstract
Introduction: Convolutional neural networks (CNNs) are machine learning tools that have great potential in the field of medical imaging. However, it is often regarded as a “black box” as the process that is used by the machine to acquire a result is not transparent. It would be valuable to find a method to be able to understand how the machine comes to its decision. Therefore, the purpose of this study is to examine how effective gradient-weighted class activation mapping (grad-CAM) visualizations are for certain layers in a CNN-based dental x-ray artifact prediction model. Methods: To tackle this project, Python code using PyTorch trained a CNN to classify dental plates as unusable or usable depending on the presence of artifacts. Furthermore, Python using PyTorch was also used to overlay grad-CAM visualizations on the given input images for various layers within the model. One image with seventeen different overlays of artifacts was used in this study. Results: In earlier layers, the model appeared to focus on general features such as lines and edges of the teeth, while in later layers, the model was more interested in detailed aspects of the image. All images that contained artifacts resulted in the model focusing on more detailed areas of the image rather than the artifacts themselves. Whereas the images without artifacts resulted in the model focusing on the visualization of areas that surrounded the teeth. Discussion and Conclusion: As subsequent layers examined more detailed aspects of the image as shown by the grad-CAM visualizations, they provided better insight into how the model processes information when it is making its classifications. Since all the images with artifacts showed similar trends in the visualizations of the various layers, it provides evidence to suggest that the location and size of the artifact does not affect the model’s pattern recognition and image classification.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.012 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".